Generally, earth-boring tools having fixed cutting elements at leading ends of the earth-boring tools, such as, for example, fixed-cutter drill bits and hybrid drill bits, may include a body having blades extending from the body. A crown of such an earth-boring tool at a leading end thereof may be defined by a cone region at and around a rotational axis, which may also be a central axis, of the tools, a nose region adjacent to and surrounding the cone region, a shoulder region adjacent to and surrounding the nose region, and a gage region at a periphery of the tool. Cutting elements may be secured to the blades at rotationally leading portions of the blades along the cone, nose, shoulder, and gage regions to engage with and remove an underlying earth formation as the earth-boring tool is rotated. Such cutting elements may comprise a polycrystalline table of superhard material, such as, for example, diamond, secured to a substrate of hard material, such as, for example, cemented tungsten carbide. The cutting elements may be secured within pockets formed in the blades, such as, for example, by brazing.
After formation, the polycrystalline tables may include catalyst material, such as, for example, cobalt, that was used to catalyze formation of inter-granular bonds between particles of the superhard material, which catalyst material may be located in interstitial spaces among interbonded grains of the superhard material. The catalyst material may be removed, such as, for example, by leaching using acid, to reduce the likelihood that differences in rates of thermal expansion between the superhard material and the catalyst material will cause cracks to form in the polycrystalline table, which may ultimately lead to chipping and premature failure of the polycrystalline table.
To further reduce the likelihood that cutting elements will prematurely fail, the types of cutting elements in different regions of the earth-boring tool may be specifically engineered to accommodate certain types of loading experienced in those regions during drilling, as disclosed in U.S. Pat. No. 5,787,022, issued Jul. 28, 1998, to Tibbitts et al., the disclosure of which is incorporated herein in its entirety by this reference. For example, the '022 patent discloses that cutting elements in the cone and nose regions may be engineered to withstand high axial and combined axial and tangential loading, and cutting elements in the shoulder and gage regions may be engineered to withstand high tangential loading. The '022 patent further discloses that cutting element design and placement may minimize and stabilize cutting element temperatures, such as, for example, by providing cutting elements in the shoulder region with internal hydraulic cooling or enhanced heat transfer characteristics.